Vine Toolkit is an open source software framework that is used to create Grid-aware web applications. One of the key concepts in Vine is its plug-in based structure: "The Vine Toolkit consists of a core project that defines a base API and programming model upon which sub projects are built. Each sub project addresses a particular problem area. Some, like the Grid Vine, build upon core Vine to define more general concepts and extensible elements. Others, like the Globus Toolkit 4 Vine, are concerned with adding support for particular third party libraries and services. Each project conforms to a particular file structure that defines how source code is built as well as how third party libraries and configuration files are packaged and deployed."